The electric motor of the axial air-gap type having a rotor having a permanent magnet, two stators arranged on both sides of the rotor in a rotation axis direction of the rotor, and an armature winding mounted to each stator is formerly known (e.g., see Japanese Patent Laid-Open No. 10-271784 and Japanese Patent Laid-Open No. 2001-136721). In accordance with such an electric motor of the axial air-gap type, relatively high output torque can be generated while the axial length of the rotor of the electric motor is shortened.
In electric conducting control of the electric motor of the axial air-gap type, an electric current is conducted to the armature windings of both the stators arranged on both the sides of the rotor in the technique described in the above publications. Thus, leakage of a magnetic flux in the armature of the stator is reduced and output torque of the electric motor can be increased.
Now, an idea that the electric motor of the axial air-gap type is also operated as an electricity generator to perform a driving operation and an electricity generating operation may come up. However, in the cited documents 1 and 2, there is no description about a construction where the electric motor of the axial air-gap type is also operated as the electricity generator. Therefore, an object of the present invention is to provide a controller able to efficiently operate the electric motor of the axial air-gap type as the electric motor and the electricity generator.